Promoted zinc titanate as catalytic agent

ABSTRACT

The catalytic hydrodesulfurization and/or hydrodenitrogenation of organic compounds containing sulfur and/or nitrogen is carried out in the presence of a catalyst composition comprising zinc, titanium and at least one promoter selected from the group consisting of vanadium, chromium, cobalt, nickel, molybdenum, tungsten, rhenium, platinum, palladium, rhodium, ruthenium, and compounds thereof.

This application is a division of application Ser. No. 125,429, filedFeb. 18, 1980, now abandoned.

This invention relates to an improved catalytic process for thehydrodesulfurization (HDS) of organic sulfur compounds orhydrodenitrogenation (HDN) of organic nitrogen compounds, and a catalysttherefor.

Hydrodesulfurization is a process intended primarily to convert thesulfur in organic sulfur compounds to hydrogen sulfide.Hydrodenitrogenation is a process intended primarily to convert thenitrogen in organic nitrogen compounds to ammonia. Hydrodesulfurizationand hydrodenitrogenation will generally occur at the same time undersimilar process conditions if both organic sulfur compounds and organicnitrogen compounds are present in the feed stream. The hydrogen sulfideand/or ammonia can be removed from the feed stream after thehydrodesulfurization and/or hydrodenitrogenation process.Hydrodesulfurization and hydrodenitrogenation are processes which aretypically utilized to remove sulfur and nitrogen from ahydrocarbon-containing feedstock which also contains organic sulfurcompounds and/or organic nitrogen compounds to produce fuels which, whenburned, will meet environmental standards. The processes may be appliedto feed streams other than hydrocarbon-containing feeds if organicsulfur compounds and/or organic nitrogen compounds are present and theremoval of sulfur and/or nitrogen is desired.

The earliest hydrodesulfurization and/or hydrodenitrogenation catalystswere bauxite and Fuller's earth. Later, catalysts containing cobaltmolybdate on alumina and nickel tungstate on alumina substantiallyreplaced the earlier catalyst and these catalysts are still used veryextensively.

Both hydrodesulfurization and hydrodenitrogenation processes requiresubstantial energy because of the elevated temperatures required andalso require substantial volumes of hydrogen which is expensive.Hydrogen is required to convert the sulfur in organic sulfur compoundsto hydrogen sulfide and to convert the nitrogen in organic nitrogencompounds of ammonia. If the feed stream containing the organic sulfurcompounds and/or organic nitrogen compounds also contains aromatics,substantial hydrogen may be consumed in hydrogenating aromatics which isundesirable. Thus, a good hydrodesulfurization or hydrodenitrogenationcatalyst is one which shows substantial activity at lower temperaturesso as to require less energy and also exhibits good selectivity for theconsumption of hydrogen so as to reduce the hydrogenation of aromaticsif aromatics are present in the feed stream which contains the organicsulfur compounds and/or organic nitrogen compounds. The reducedhydrogenation of aromatics results in a lower consumption of hydrogenand a higher quality desulfurized and/or denitrogenized aromaticcontaining feedstock.

It is thus an object of this invention to provide an improvedhydrodesulfurization and/or hydrodenitrogenation catalyst which exhibitshigh activity and good selectivity to thus provide an improved processfor the hydrodesulfurization of organic sulfur compounds orhydrodenitrogenation of organic nitrogen compounds.

In accordance with the present invention, a catalyst compositioncomprising zinc, titanium and a promoter is utilized as a catalyst in ahydrodesulfurization process and/or hydrodenitrogenation process. Thepromoter is at least one member selected from the group consisting ofvanadium, chromium, cobalt, nickel, molybdenum, tungsten, rhenium,platinum, palladium, rhodium, ruthenium and, compounds thereof. Thehydrodesulfurization and/or hydrodenitrogenation process is carried outunder suitable conditions. The catalyst composition exhibits substantialactivity for hydrodesulfurization and/or hydrodenitrogenation and alsoexhibits improved selectivity for the consumption of hydrogen over theconventional cobalt molybdate on alumina catalyst. This results in adecreased hydrogenation of aromatics, where aromatics are present, whichreduces the volume of hydrogen required by the hydrodesulfurizationand/or hydrodenitrogenation process.

The hydrodesulfurization and/or hydrodenitrogenation process ispreferably carried out in cycles comprising a reaction period and aregeneration period for the catalyst. The reaction period comprisescontacting a feedstock which contains organic sulfuric compounds and/ororganic nitrogen compounds with the catalyst to thereby convert thesulfur in organic sulfur compounds in the feedstock to hydrogen sulfideand also convert the nitrogen in organic nitrogen compounds of ammonia.After the reaction period, a molecular oxygen-containing gas is passedin contact with the catalyst to regenerate the catalyst by burning offcarbonaceous materials which may have formed on the catalyst.

Other objects and advantages of the invention will be apparent from theforegoing brief description of the invention and the appended claims, aswell as the detailed description of the invention which follows.

Any suitable organic sulfur compound may be hydrodesulfurized inaccordance with the present invention. Suitable organic sulfur compoundsinclude sulfides, disulfides, mercaptans, thiophenes, benzothiophenes,dibenzothiophenes and the like and mixtures of two or more thereof.

Any suitable organic nitrogen compound may be hydrodenitrogenized inaccordance with the present invention. Suitable organic nitrogencompounds include amines, diamines, pyridines, quinolines, porphyrins,benzoquinolines and the like and mixtures of two or more thereof.

Organic sulfur compounds and/or organic nitrogen compounds contained inany suitable gaseous stream may be hydrodesulfurized and/orhydrodenitrogenized in accordance with the present invention. Suitablegaseous streams include light hydrocarbons such as methane, ethane,ethylene and natural gas, gases such as hydrogen and nitrogen, gaseousoxides of carbon, steam, and the inert gases such as helium and argon.

The invention is particularly directed to hydrocarbon-containing feedstreams which also contain organic sulfur compounds and/or organicnitrogen compounds. Suitable hydrocarbon-containing feeds include notonly those feeds previously mentioned but also petroleum products andproducts from extraction and/or liquefaction of coal and lignite,products from tar sands, products from shale oil and similar products.Suitable hydrocarbons include naphtha, distillates, gas oil having aboiling range from about 205° to about 538° C., topped crude having aboiling range in excess of about 343° C. and residuum.

The catalyst employed in the process of the present invention is acomposition comprising zinc, titanium and a promoter. At least onemember of the promoter is selected from the group consisting ofvanadium, chromium, cobalt, nickel, molybdenum, tungsten, rhenium,platinum, palladium, rhodium, ruthenium, and compounds thereof. Thepromoting elements are generally present on the catalyst as the oxide orthe sulfide except for platinum which will generally be present as theelement. The zinc and titanium are generally present as zinc titanate.

The zinc titanate base of the catalyst compositon may be prepared byintimately mixing suitable portions of zinc oxide and titanium dioxide,preferably in a liquid such as water, and calcining the resultingmixture in a gas containing molecular oxygen at a temperature in therange of about 650° C. to about 1050° C., preferably in the range ofabout 675° C. to about 975° C. A calcining temperature in the range ofabout 800° C. to about 850° C. is most preferred because the surfacearea of the catalyst is maximized in this temperature range thusproducing a more active catalyst. The titanium dioxide used in preparedthe zinc titanate preferably has extremely fine particle size to promoteintimate mixing of the zinc oxide and titanium dioxide. This produces arapid reaction of the zinc oxide and titanium dioxide which results in amore active catalyst. Preferably the titanium dioxide has an averageparticle size of less than 100 millimicrons and more preferably lessthan 30 millimicrons. Flame hydrolyzed titanium dioxide has extremelysmall particle size and is particularly preferred in preparing thecatalyst. The atomic ratio of zinc to titanium can be any suitableratio. The atomic ratio of zinc to titanium will generally lie in therange of about 1:1 to about 3:1 and will preferably lie in the range ofabout 1.8:1 to about 2.2:1 because the activity of the catalyst isgreatest for atomic ratios of zinc to titanium in this range. The term"zinc titanate" is used regardless of the atomic ratio of zinc totitanium.

The zinc titanate base of the catalyst composition may also be preparedby coprecipitation from aqueous solutions of a zinc compound and atitanium compound. The aqueous solutions are mixed together and thehydroxides are precipitated by the addition of an alkali metalhydroxide. The precipitate is then washed, dried and calcined, asdescribed in the preceding paragraph, to form zinc titanate. This methodof preparation is less preferred than the mixing method because the zinctitanate prepared by the coprecipitation method is softer than the zinctitanate prepared by the mixing method.

The promoter, at least one member of which is selected from the groupconsisting of vanadium, chromium, cobalt, nickel, molybdenum, tungsten,rhenium, platinum, palladium, rhodium, ruthenium and compounds thereof,is generally present on the catalyst in the oxide or sulfide form exceptfor platinum which will generally be present in the elemental form. Thepromoter can be added to the zinc titanate by any method known in theart. The promoter can be added to the zinc titanate as powdered oxideand dispersed by any method known in the art such as rolling, shaking orstirring. For ease of preparation, the preferred method of adding thepromoter is by impregnating the preformed zinc titanate with a solutionof a compound of the promoting element that becomes converted to theoxide during the subsequent preparation of the catalyst. The impregnatedcatalyst is dried to remove solvent and is then heated in air at atemperature in the range of about 500° C. to about 650° C., preferablyabout 540° C. If more than one of the promoting elements is to be usedin the catalyst composition, the catalyst composition is preferablydried and calcined after each addition of a promoting element.

The concentration of the promoter can be any suitable concentration. Theconcentration of the total promoter, expressed as an element, willgenerally range from about 0.1 to about 24 weight percent based on theweight of the catalyst composition. The concentration of the vanadium,chromium, cobalt, nickel, molybdenum, or tungsten as individualpromoting elements, expressed as an element, if present, will preferablybe in the range of about 0.1 to about 16 weight percent based on theweight of the catalyst composition and will more preferably be in therange of about 1.6 to about 8 weight percent. The concentration ofrhenium, palladium, rhodium, ruthenium or platinum as individualpromoting elements, expressed as the element, if present, willpreferably be in the range of about 0.2 to about 1.6 weight percent.

Either the elemental form of the promoters or any suitable compound ofthe promoters may be used to form the catalyst composition.

Vanadium compounds suitable for use as a promoter include di-, tri-,tetra-, and pentavalent vanadium oxides, vanadium (III) sulfide,vanadium (IV) oxide sulfate, ammonium metavanadate, sodium metavanadate,and the like and mixtures of any two or more thereof.

Chromium compounds suitable for use as a promoter include ammoniumchromate and ammonium dichromate, chromic nitrate, chromium (III) oxide,chromium (VI) oxide, chromic sulfate, potassium chromate and potassiumdichromate, chromic acetate, and the like and mixtures of any two ormore thereof.

Cobalt compounds suitable for use as a promoter include cobalt acetate,cobalt carbonate, cobalt nitrate, cobalt oxide, cobalt sulfate, cobaltthiocyanate, and the like and mixtures of any two or more thereof.

Nickel compounds suitable for use as a promoter include nickel acetate,nickel carbonate, nickel nitrate, nickel oxide, nickel sulfate, ammoniumnickel sulfate, nickel sulfamate, and the like and mixtures of any twoor more thereof.

Molybdenum compounds suitable for use as a promoter include ammoniummolybdate, ammonium heptamolybdate, sodium molybdate, potassiummolybdate, molybdenum oxides such as molybdenum (IV) oxide andmolybdenum (VI) oxide, molybdenum sulfide, and the like and mixtures ofany two or more thereof.

Tungsten compounds suitable for use as a promoter include ammoniumtungstates such as ammonium metatungstate and ammonium paratungstate,tungsten oxides such as tungsten (IV) oxide and tungsten (VI) oxide,tungsten sulfides such as tungsten (IV) sulfide and tungsten (VI)sulfide, heteropoly acids such as tungstophosphoric acid andtungstosilicic acid, and the like and mixtures of any two or morethereof.

Rhenium compounds suitable for use as a promoter include perrhenic acid,ammonium perrhenate, rhenium oxides such as rhenium (VI) oxide andrhenium (VII) oxide, rhenium sulfide, and the like and mixtures of anytwo or more thereof.

Platinum compounds suitable for use as a promoter include dihydrogenhexachloroplatinate, diamineplatinum (II) nitrate, tetraamineplatinum(II) nitrate, and the like and mixtures of any two or more thereof.

Ruthenium, rhodium, and palladium nitrates are a suitable form for theaddition of these elements as catalyst promoters.

Halogen-containing compounds of the promoting elements can be used aspromoters. However, the user should be aware of the possibility ofcorrosion caused by their presence.

A combination of cobalt and molybdenum is presently the most preferredpromoter because of the improved selectivity of a catalyst compositionemploying this promoter. Especially preferred are catalyst compositionsin which the cobalt:molybdenum atomic ratio is in the range of about 0.6to about 0.8.

The surface area of the catalyst increases as the catalyst becomessulfided and reaches a maximum when the catalyst is completely sulfided.The catalyst may become sulfided during the hydrodesulfurization processor may be presulfided. The catalyst is preferably presulfided even ifthe catalyst is to be used only for hydrodenitrogenation. Thepresulfiding of the catalyst is preferred before the catalyst isinitially used and after each regeneration of the catalyst. Preferably,the catalyst is presulfided in two steps. The catalyst is first treatedwith a mixture of hydrogen sulfide in hydrogen at a temperature in therange of about 175° C. to about 225° C., preferably about 205° C. Thetemperature in the catalyst composition will rise during this firstpresulfiding step and the first presulfiding step is continued until thetemperature rise in the catalyst has substantially stopped or untilhydrogen sulfide is detected in the effluent flowing from the reactor.The mixture of hydrogen sulfide and hydrogen preferably contains in therange of about 5 to about 20 mole percent hydrogen sulfide, preferablyabout 10 mole percent hydrogen sulfide.

The second step in the presulfiding process consists of repeating thefirst step at a temperature in the range of about 350° C. to about 400°C., preferably about 370° C. It is noted that other mixtures containinghydrogen sulfide may be utilized to presulfide the catalyst. Also theuse of hydrogen sulfide is not required. In a commercial operation, itis common to utilize a light naphtha containing sulfur to presulfide thecatalyst.

The pre-sulfided form is the most active state of the catalyst. However,since the zinc titanate base of the catalyst becomes sulfided up toabout 25 weight percent of the catalyst, the presulfiding time asdescribed above might be too lengthy to be practical in a commercialoperation. An alternative method is sulfiding with the feed to beprocessed at mild conditions where coke formation on the catalyst isminimal. The feed is preferably recycled until the desired sulfurcontent is reached, and the gaseous effluent containing hydrogen sulfideis also recycled. When the desired catalyst activity is reached therecycle operation is discontinued.

The process of this invention can be carried out by means of anyapparatus whereby there is achieved a contact with the catalyst of theorganic compounds to be hydrodesulfurized and/or hydrodenitrogenized.The process is in no way limited to the use of a particular apparatus.The process of this invention can be carried out using a fixed catalystbed, fluidized catalyst bed, or moving catalyst bed. Presently preferredis a fixed catalyst bed.

In order to avoid any casual mixing of the feed stream containing theorganic sulfur compound and/or organic nitrogen compound and theoxygen-containing fluid utilized in the regeneration step, provision ispreferably made for terminating the flow of feed to the reactor andsubsequently injecting an inert purging fluid such as nitrogen, carbondioxide or steam. Any suitable purge time can be utilized. The purgeduration will generally be of sufficient duration to remove allhydrocarbons and hydrogen from the system. Any suitable flow rate of thepurge gas may be utilized. Presently preferred is a purge fluid flowrate in the range of about 800 GHSV to about 1200 GHSV.

Any suitable temperature for hydrodesulfurization and/orhydrodenitrogenation of the organic sulfur compounds and/or organicnitrogen compounds over the catalyst composition of the presentinvention can be utilized. The temperature will generally be in a rangeof about 205° C. to about 538° C. and will more preferably be in therange of about 316° C. to about 427° C. for the hydrodesulfurizationprocess and/or the hydrodenitrogenation process.

Any suitable pressure for the hydrodesulfurization and/orhydrodenitrogenation of the organic sulfur compounds and/or organicnitrogen compounds over the catalyst composition of the presentinvention can be utilized. In general, the pressure will be in the rangeof about 200 to about 3000 psig total system pressure for thehydrodesulfurization process and/or the hydrodenitrogenation process.The total system pressure is the sum of the partial pressure of thefeedstock plus the partial pressure of the added hydrogen. Preferablythe total system pressure will range from about 400 to about 1000 psigfor the hydrodesulfurization process and/or the hydrodenitrogenationprocess.

Any suitable quantity of hydrogen can be added to thehydrodesulfurization and/or hydrodenitrogenation process. The quantityof hydrogen used to contact the feedstock containing the organiccompounds being hydrodesulfurized and/or hydrodenitrogenized will be inthe range from about 100 to about 10,000 SCF/bbl and will morepreferably be in the range from about 500 to about 3000 SCF/bbl.

Any suitable residence time for the feedstock in the presence of thecatalyst composition of the present invention can be utilized. Ingeneral, the residence time in terms of the volumes of liquid per volumeof catalyst per hour (LHSV) can range from about 0.1 to about 20 andwill more preferably range from about 1 to about 5 for thehydrodesulfurization process and/or the hydrodenitrogenation process.

To maintain the activity of the catalyst, the temperature of thehydrodesulfurization and/or hydrodenitrogenation process is graduallyincreased to compensate for loss of catalyst activity due to fouling ofthe catalyst. When the temperature of the hydrodesulfurization and/orhydrodenitrogenation process cannot conveniently be increased further,the catalyst is typically regenerated by terminating the flow of feed tothe reactor and purging with an inert gas such as nitrogen to removecombustibles and then introducing free oxygen-containing fluid tooxidize the carbonaceous deposits which have formed on the catalystduring the hydrodesulfurization and/or hydrodenitrogenation process. Thecatalyst will generally be utilized for a year or longer before beingregenerated.

The amount of oxygen, from any source, supplied during the regenerationstep will be sufficient to remove carbonaceous materials from thecatalyst and will preferably be in 1-5 mole percent concentration. Theregeneration step is conducted at generally the same pressure recitedfor the hydrodesulfurization and/or hydrodenitrogenation step but can becarried out at lower pressure if desired. The temperature for theregeneration step is preferably maintain in the range of about 425° C.to about 540° C., although it can be as high as 620° C. If thehydrodesulfurization and/or hydrodenitrogenation process has beenproceeding at a temperature lower than 425° C., the temperature of thecatalyst should be increased to about 425° C. prior to the start of theregeneration of the catalyst in order to remove any carbonaceousdeposits on the catalyst within a reasonable time. Regeneration willalso partially convert the sulfided catalyst to the oxide form and thepre-sulfiding step should be repeated.

The following example is presented in further illustration of theinvention.

EXAMPLE Preparation of Catalysts

Zinc titanate was prepared by combining 162.8 g (2 moles) ofMallinckrodt zinc oxide with 79.9 g (one mole) of Cab-O-Ti titaniumdioxide in 1200 ml of water and mixing for 10 minutes in a blender. Theresulting slurry was dried in an oven at 105° C. and then calcined byheating in air at 816° C. for three hours. After cooling, the calcinedsolid was crushed and screened. A -16+40 mesh portion of the thusscreened catalyst, designated catalyst A, was reserved for testing asmade and was also utilized in the preparation of catalyst B, C, E-H, andJ-Q. The atomic ratio of zinc to titanium in catalyst A, B, C, E-H andJ-Q was 2.00:1.

Zinc titanate was also prepared by mixing 175.4 g (1.8 mole) of poweredzinc sulfide and 79.9 g (1.0 mole) of Degussa flame hydrolyzed titaniumdioxide in water for about 10 minutes. The resulting mixture was driedin an oven at 120° C. to remove the water and was then calcined in airfor 4 hours at 815° C. After cooling, the resultant zinc titanate wascrushed and a -16+40 mesh portion was separated by screening and used inthe preparation of catalyst D and I. The atomic ratio of zinc totitanium in catalyst D and I was 1.8:1.

The general method for preparing catalyst B-Q was as follows. A weighedportion of previously dried zinc titanate having a known pore volume wascovered with a solution (generally aqueous) of known concentration ofthe promoting element. After standing one hour at 25° C. temperature,excess solution was removed by decanting or filtering and the wetcatalyst was dried, with occasional stirring, in an oven, on a hotplate, or under a heat lamp. The dried catalyst was calcined in air in amuffle furnace for 3-4 hours at 538° C., cooled in a desiccator, andreweighed. The quantity of promoter added by this procedure was assumedto be calculable from the volume of promoter solution contained in thepores of the zinc titanate, i.e., its pore volume. Occasionally thisquantity was checked by observing the gain in weight of the catalystmade as described, but this gain was not considered to provide adefinitive value of concentration. The finished catalysts werechemically analyzed for promoter concentration and surface area. To addmore than one promoter, the entire procedure previously described wasrepeated for each impregnation.

The concentration of promoter solution used to impregnate zinc titanatefor a desired promoter level was calculated from the formula ##EQU1##where n=number of atoms of promoter element per molecule of promotercompound. To illustrate, to prepare a catalyst containing 8.0 weightpercent molybdenum on zinc titanate that has 0.8 cc/g pore volume, usingammonium heptamolybdate tetrahydrate as the source of molybdenum,##EQU2##

The composition of catalyst B-Q and the surface area of catalyst B-Q, ifmeasured, are summarized in Table I. In every case zinc titanatecomprises the remainder of the analysis.

                  TABLE I                                                         ______________________________________                                        Catalyst                                                                              Promoters, Wt. %  Surface Area, m.sup.2 g.sup.-1                      ______________________________________                                        B       13.0 MoO.sub.3    5.1                                                 C       2.6 Re.sub.2 O.sub.7                                                                            --                                                  D       2.6 Re.sub.2 O.sub.7                                                                            --                                                  E       10.7 V.sub.2 O.sub.5                                                                            --                                                  F       10.2 CoO          --                                                  G       4.0 NiO, 13.0 MoO.sub.3                                                                         4.3                                                 H       4.0 NiO, 13.0 MoO.sub.3                                                                         6.0                                                 I       3.4 CoO, 14.7 MoO.sub.3                                                                         8.6                                                 J       4.2 CoO, 9.63 MoO.sub.3                                                                         12.1                                                K       2.8 CoO, 7.95 MoO.sub.3                                                                         5.9                                                 L       5.21 CoO, 13.35 MoO.sub.3                                                                       6.5                                                 M       0.38 CoO, 0.87 MoO.sub.3                                                                        6.4                                                 N       10.7 V.sub.2 O.sub.5, 4.5 MoO.sub.3                                                             --                                                  O       7.6 NiO, 24.0 WO.sub.3                                                                          --                                                  P       5.9 Cr.sub.2 O.sub.3                                                                            --                                                  Q       1.0 Pt, 3.5 CoO, 12.5 MoO.sub.3                                                                 --                                                  ______________________________________                                    

The promoters were added as aqueous solutions of the following salts:Molybdenum as (NH₄)₆ Mo₇ O₂₄.4 H₂ O, rhenium as NH₄ ReO₄, vanadium asNH₄ VO₃, cobalt as Co(NO₃)₂.6 H₂ O, nickel as Ni(NO₃)₂.6 H₂ O, tungstenas (NH₄)₂ W₄ O₁₃.8H₂ O, chromium as Cr(NO₃)₃.9H₂ O, and platinum as H₂PtCl₆.

Testing Procedure

All catalysts were evaluated in an automated test unit capable oftesting six catalysts simultaneously. Six reactors, 1" o.d.×0.813" i.d.and made of 316 stainless steel, were disposed symmetrically in a singlefurnace. Each of the six reactors was operated with a fixed catalyst bedin down-flow mode. Oil preheat lines ran upflow through the furnace,entering the top of the respective reactor where the oil was mixed withadded hydrogen. Conditions in the reactors were mixed phase, i.e.,trickle bed process. Runs were made with 25 cc of catalyst, or with 5 ccof catalyst diluted with 20 cc of inert diluent (corumdum). Contact timeof reactants with catalyst, in terms of the volume of oil per volume ofcatalyst per hour (LHSV), was varied by either varying the oil pumpsettings or by the use of diluted catalyst.

The procedures generally followed to evaluate a catalyst was to make atemperature survey. After a "break-in" period during which the catalystwas sulfided with feed or with a hydrogen sulfide-hydrogen mixture (thelatter being preferred), the catalyst was utilized in the temperaturerange 316°-427° C. (600°-800° F.). The sequence of tests frequently usedwas 750° F., 800° F., 600° F., 700° F., and 750° F. Comparison of thefirst and last tests indicated if any changes in activity occurredduring the survey. Catalyst activities were then compared using atemperature versus hydrodesulfurization-hydrodenitrogenationcorrelation. During a run liquid products were removed from a highpressure separator. The liquid products were analyzed for carbon,hydrogen, nitrogen, and sulfur and for hydrocarbon type. At the end of arun or when a unit was shut down overnight, the reactor was purged forabout an hour with hydrogen after pumping of liquid feed had beenstopped. Carbon deposited on used catalyst was determined by analysis ofa representative sample after all catalyst had been removed from thereactor. Catalyst regeneration was normally done by calcining thematerial in air in a muffle furnace at about 427°-538° C. for 1 to 2hours. Usually at least two sets of runs were made on each catalyst todetermine any effects of regeneration.

Two different methods were used to prepare the catalyst for testing,referred to as the "break-in" period above. Both involved sulfiding thecatalyst. One sulfiding method utilized operation at reaction conditionswith a sulfur-containing feed for a period of time sufficient to sulfidethe catalyst with hydrogen sulfide derived from the feed. The othersulfiding method involved treating the catalyst with 5-10 mole percenthydrogen sulfide in hydrogen at atmospheric pressure. Catalysttemperature between 315°-400° C. was maintained during the sulfidingperiod when using the first method. As described above, presulfidingwith H₂ S/H₂ mixture was done in two steps: first at 175°-225° C., thenat 350°-400° C.

In general, process conditions used to evaluate the hydrodesulfurizationactivity of these catalysts included 0-1200 psig pressure, 260°-427° C.temperature, liquid feed rates of 0.5-10 LHSV, and hydrogen feed rate of5000 SCF/bbl (9.5 mole hydrogen/mole oil).

Results of Catalyst Tests

Catalyst C (rhenium on zinc titanate) and Shell-344 were tested underidentical conditions to compare their hydrotreating activity. Shell-344is a commercially produced cobalt molybdate on alumina hydrotreatingcatalyst. By analysis, the Shell-344 tested had the following pertinentcharacteristics: 0.79 g/cc bulk density, 0.5 cc/g pore volume, 186 m² /gsurface area, and it contained 2.99 weight percent cobalt as CoO and14.42 weight percent molybdenum as MoO₃. For the comparison, gas oilserved as the feedstock. The gas oil contained 0.2 weight percentorganic sulfur, 470 ppm organic nitrogen, 68 percent naphthenes plusaromatics, and had a boiling range of 260°-510° C. Tests were made at427° C., 1000 psig, 1.0 LHSV, and 5000 SCH H₂ /bbl. Table II summarizestest results.

                  TABLE II                                                        ______________________________________                                        Catalyst            C      Shell-344                                          ______________________________________                                        Hydrodesulfurization,                                                         wt. %               92     95                                                 Hydrodenitrogenation,                                                         wt. %               65     96                                                 Yield of <260° C., wt. %                                                                   10     29                                                 Naphthenes + aromatics,                                                       wt. %               71     66                                                 Wt. % H in product  13.21  13.38                                              ______________________________________                                    

While catalyst C was substantially inferior for hydrodenitrogenation itwas nearly equal for hydrodesulfurization. Catalyst C consumedsignificantly less hydrogen than the commercial cobalt molybdate onalumina. This is demonstrated by the lower yield of hydrocrackedproduct, by the higher concentration of naphthenes plus aromatics, andby the lower concentration of hydrogen in the liquid product as shown byelemental analysis.

Catalyst H and Shell-344 were tested under identical conditions tohydrotreat a distillate that, by analysis, contained 13.05 weightpercent hydrogen, 7700 ppm organic sulfur, 124 ppm organic nitrogen, 31weight percent aromatics, and a mono/poly aromatics ratio (weight) of0.9. Tests were made at 1000 psig, 1.0 LHSV, and 5000 SCF H₂ /bbl. Otherconditions and test results are summarized in Table III.

                  TABLE III                                                       ______________________________________                                        Catalyst       H            Shell-344                                         ______________________________________                                        Temp., °F.                                                                            725      775     725    775                                    Hydrodesulfurization,                                                         wt. %          97.5     99.2    98.7   99.0                                   Hydrodenitrogenation,                                                         wt. %          96.6     95.2    97.6   99.2                                   Yield of <260° C., wt. %                                                              8.7      13.8    21.5   25.0                                   H in product, wt. %                                                                          13.35    13.36   13.60  13.42                                  S in product, ppm                                                                            190      60      100    80                                     N in product, ppm                                                                            4        6       3      1                                      Aromatics, wt. %                                                                             31       30      26     28                                     Mono/poly aromatics                                                                          2.4      2.6     5.5    5.5                                    ______________________________________                                    

At both temperatures the Shell-344 catalyst was generally slightlysuperior for both hydrodesulfurization and hydrodenitrogenationactivity. However, catalyst H consumed less hydrogen as evidenced by theextent of hydrocracking and by the hydrogen content of the product.Additionally, lower hydrogen consumption is deduced from the aromaticscontent and the production of mono aromatics from poly aromatics.

Table IV summarizes results of runs in which promoted catalysts, B, C,D, E, F, G, N, O, P and Q as well as unpromoted catalysts A and A'(different preparations of same catalyst) were used to hydrotreat thefeedstock blend. Unpromoted catalyst A' was prepared in the same manneras unpromoted catalyst A. All of the tests were made at 1.0 LHSV with5000 SCF H₂ /bbl and were of 30-60 hours duration. With the possibleexception of catalysts E and P, each of the promoted zinc titanates wasmore active for HDS and HDN than catalysts A and A'--the unpromoted zinctitanate. The presence of vanadium in catalyst E is principally of valueto regenerate the spent catalyst. Catalyst G, containing both nickel andmolybdenum, is superior at any given temperature to any of the singlypromoted zinc titanates of Table IV for hydrodesulfurization activity;it is at least equal in hydrodenitrogenation activity to any of thesingly promoted catalysts.

                                      TABLE IV                                    __________________________________________________________________________    Run              1  2  3  4  5  6   7  8  9  10 11 12 13 14 15                Catalyst         A  A  A' A' B  B   C  D  E  F  G  N  O  P  Q                 __________________________________________________________________________    Pressure, psig   500                                                                              500                                                                              1000                                                                             500                                                                              500                                                                              1000                                                                              500                                                                              500                                                                              500                                                                              500                                                                              500                                                                              500                                                                              500                                                                              500                                                                              500               Wt. % Hydrodesulfurization                                                    at 600° F.                   32.8                                                                             37.5     57.3                          at 650° F.                                                                              28.0                                                                             33.3                                                                             35.1                                                                             31.9                                                                             47.2                                                                             62.3                                                                              48.0                                                                             54.7                                                                             31.5                                                                             39.7                                                                             94.3                                                                             52.1                                                                             78.7                                                                             22.2                                                                             72.0              at 700° F.                                                                              46.7        77.8                                                                             84.4                                                                              70.1                                                                             77.6                                                                             46.6                                                                             54.8                                                                             97.3                                                                             71.2                                                                             91.2                                                                             31.9                                                                             84.0              at 725° F.      51.9                                                                             44.4                                                at 750° F.                                                                              54.7                                                                             60.0                                                                             66.2     96.5                                                                              84.3                                                                             89.7                                                                             65.8                                                                             71.2                                                                             98.7                                                                             89.6                                                                             94.7                                                                             45.8                                                                             88.0              at 775° F.                                                                              66.7                                                                             70.7                                                                             79.2                                                                             63.9                                                                             87.5                                                                             96.2      68.5                                                                             82.2  93.6                                                                             93.3                                                                             56.9                                                                             93.3              at 800° F.      83.1     99.1                                                                              96.5                                                                             96.4     99.5                          Wt. % Hydrodenitrogenation                                                    at 600° F.                   79.1                                                                             78.6     73.2                          at 650° F.                                                                              73.2                                                                             61.4                                                                             85.5                                                                             63.2                                                                             71.8                                                                             93.5                                                                              86.6                                                                             87.7                                                                             57.6                                                                             70.0                                                                             94.1                                                                             77.2                                                                             79.5                                                                             57.0                                                                             74.5              at 700° F.                                                                              78.4                                                                             71.9                                                                             81.5     98.9                                                                              92.5                                                                             91.4                                                                             67.3                                                                             73.1                                                                             97.4                                                                             82.0                                                                             84.8                                                                             64.8                                                                             83.0              at 750° F.                                                                              74.5                                                                             66.0                                                                             87.9     100.0                                                                             88.2                                                                             95.2                                                                             72.1                                                                             73.0                                                                             98.0                                                                             82.9                                                                             88.4                                                                             70.3                                                                             79.7              at 775° F.                                                                              75.8                                                                             77.1                                                                             92.7     97.6      77.9                                                                             75.1  87.3                                                                             77.7                                                                             70.3                                                                             77.8              at 800° F.      96.8     100.0                                                                             86.6                                                                             94.1     96.7                          Catalyst Inspection                                                           Carbon after run, wt. %                                                                        0.30                                                                             0.57                                                                             0.33                                                                             0.43                                                                             0.47                                                                             0.45                                                                              0.34                                                                             0.73                                                                             0.56                                                                             0.38                                                                             0.82                                                                             0.58                                                                             0.39                                                                             0.70                                                                             0.56              Surface area, m.sup.2 /g                                                      After run                           14.2                                                                             21.1     17.6                          After regeneration        10.5      6.9                                                                              7.4      7.0                           __________________________________________________________________________     *Carbon after regeneration was believed to be zero weight percent.       

Table V summarizes results from runs made with five differentcatalysts--all being cobalt molybdate on zinc titanate but differing inmethod of zinc titanate preparation or in their concentration of cobaltand molybdenum. These catalysts represent a preferred embodiment of thisinvention. All runs were made with a refinery blend of 70% straight rundistillate and 30% light cycle oil. The mixture contained 0.75 weightpercent organic sulfur, 220 ppm organic nitrogen, and had a boilingrange of 99°-382° C. Referring to Table V runs 21-22 and runs 23-24illustrate the effect of varying contact time (LHSV). The effect ofcontact time is much larger for hydrodenitrogenation activity than it isfor hydrodesulfurization activity. Runs 16-17 compare the effect of twodifferent pressures; at constant temperature the higher pressure alwaysincreases both hydrodesulfurization and hydrodenitrogenation. Runs 17-18and 19-21 compare the effect of varying the number of process andregeneration cycles on a given catalyst. Runs 17-18 and 19-21 indicatethat the catalyst's activity does not change markedly when the number ofprocess and regeneration cycles is varied. Runs 19-20 compare the effectof varying the length of the process cycles. After 285 hours, comparedwith 37 hours, the catalyst has lost a little hydrodesulfurizationactivity--but considerably more hydrodenitrogenation activity.

                                      TABLE V                                     __________________________________________________________________________    Run        16   17  18  19  20  21  22  23  24  25   26   27                  Catalyst   H    H   H   I   I   I   I   J   J   K    L    L                   __________________________________________________________________________    No. times regenerated                                                                    0    2   4   0   1   2   4   2   2   1    0    1                   Presulfided with                                                                         Feed Feed                                                                              Feed                                                                              Feed                                                                              Feed                                                                              Feed                                                                              Feed                                                                              Feed                                                                              Feed                                                                              H.sub.2 S/H.sub.2                                                                  H.sub.2 S/H.sub.2                                                                  H.sub.2                                                                       S/H.sub.2           Run Conditions                                                                Pres., psig                                                                              1000 500 500 500 500 500 500 500 500 500  500  500                 LHSV       1.0  1.0 1.0 1.0 1.0 1.0 2.5 1.0 2.5 1.0  1.0  1.0                 Reaction time since                                                           regenerated, hrs.                                                                        36   36  36  37  285 48  73  37  99  17   17   17                  Wt. %                                                                         Hydrodesulfurization                                                          at 600° F.               61.3                                                                              68.0    61.3                                                                              78.4 61.5 77.7                at 650° F.                                                                        90.0 81.9                                                                              80.0                                                                              93.3                                                                              88.0                                                                              88.0                                                                              84.0                                                                              88.0                                                                              77.3                                                                              91.7 76.3 91.7                at 700° F.                                                                        95.3 92.4                                                                              90.7                                                                              98.7                                                                              92.9                                                                              94.7                                                                              90.7                                                                              94.7                                                                              86.7                                                                              98.3 89.3 97.9                at 750° F.                                                                        98.6 97.4                                                                              97.3                                                                              94.7                                                                              96.8                                                                              98.7                                                                              96.0                                                                              97.3                                                                              96.0                                                                              98.9 94.0 98.5                at 775° F.                                                                        99.2 97.4                                                                              98.9                                                                              99.6                                                                              96.5                                                                              99.2    99.1                                  at 800° F.                   97.3    96.0                                                                              99.4 96.9 99.2                Wt. %                                                                         Hydrodenitrogenation                                                          at 600° F.               69.9                                                                              37.8    56.5                                                                              85.0 66.3 82.9                at 650° F.                                                                        96.8 94.9                                                                              88.0                                                                              97.1                                                                              71.9                                                                              90.8                                                                              43.9                                                                              86.9                                                                              56.1                                                                              90.9 64.2 85.6                at 700° F.                                                                        98.0 86.7                                                                              86.7                                                                              97.8                                                                              70.6                                                                              93.5                                                                              46.3                                                                              96.7                                                                              56.5                                                                              97.3 75.9 98.9                at 750° F.                                                                        100.0                                                                              86.7                                                                              86.7                                                                              94.9                                                                              75.2                                                                              95.4                                                                              78.5                                                                              83.7                                                                              78.0                                                                              93.0 81.4 90.9                at 775° F.                                                                        95.2 91.4                                                                              91.3                                                                              96.4                                                                              71.2        94.8                                  at 800° F.                                                                        100.0                90.2                                                                              77.6    63.1                                                                              93.0 77.5 92.5                Catalyst inspection                                                           Carbon, wt. %                                                                            0.42 0.46                                                                              0.64                                                                              0.65                                                                              0.39                                                                              0.58    0.84    0.83 0.60 0.64                Surface area, m.sup.2 /g                                                      After run       13.5                                                                              7.2     10.4                                                                              9.2     13.2    21.1 12.5 16.0                After regen.    4.9 4.3                 7.0     8.5  5.6                      __________________________________________________________________________     *Carbon after regeneration was believed to be zero weight percent.       

It was previously stated that the atomic ratio Co:Mo of about 0.6-0.8:1was the preferred combination of these promoters on zinc titanate. TableVI tabulates results of runs with catalysts K, L, and M which containedthe promoters in approximately this ratio but at widely differentpromoter concentrations. All runs reported there were made at 500 psig,1.0 LHSV using the refinery blend feedstock, used to obtain the resultsset forth in Table V, with catalysts that had been pre-sulfided with ahydrogen sulfide-hydrogen gas mixture in the manner previouslydescribed. As shown in Table I, catalysts K, L, and M contained 10.75,18.56, and 1.25 weight percent of (CoO+MoO₃), respectively. The activityof catalysts K and L for HDS and HDN recorded in Table VI shows them tobe essentially the same; in contrast catalyst M, which contained muchlower concentration of promoter, exhibited substantially less activity.

                  TABLE VI                                                        ______________________________________                                        Run       28     29     30    31   32   33   34                               Catalyst  K      K      K     L    L    M    M                                ______________________________________                                        No. times 0      1      2     0    1    0    1                                regenerated                                                                   % HDS at                                                                      600° F.                                                                          52.7   78.4   76.7  61.5 77.7 39.2 36.1                             650       71.5   91.7   89.9  76.3 91.7 56.7 49.7                             700       86.8   98.3   97.6  89.3 97.9 71.5 72.0                             750       95.7   99.6   97.2  96.1 99.3 84.9 85.2                             750       92.5   98.9   98.9  94.0 99.2 85.7 82.8                             800       96.5   99.4   98.0  96.9 98.5 90.4 90.7                             % HDN at                                                                      600° F.                                                                          69.5   85.0   87.7  66.3 82.9 57.8 73.8                             650       66.8   90.9   90.9  64.2 85.6 75.4 61.0                             700       78.6   97.3   97.9  75.9 98.9 74.9 84.5                             750       88.8   98.9   100.0 84.5 98.9 74.3 93.0                             750       79.1   93.0   96.8  81.8 90.9 70.1 76.5                             800       80.7   93.0   98.9  77.5 92.5 67.9 89.8                             Catalyst                                                                      inspection                                                                    Carbon, wt. %                                                                           0.46   0.83   1.01  0.60 0.64 0.66 0.44                             Surface area,                                                                 m.sup.2 /g                                                                    After run 13.3   18.7   20.1  12.5 16.0 16.2 17.2                             After regen.                                                                            6.6    8.5          5.6       6.2                                   ______________________________________                                         *Carbon after regeneration was believed to be zero weight percent.       

Reasonable variations and modifications are possible within the scope ofthe disclosure and the appended claims to the invention.

That which is claimed is:
 1. A catalyst composition comprising zinc,titanium, and at least one promoter selected from the group consistingof vanadium, chromium, cobalt, molybdenum, tungsten, platinum,palladium, rhodium, ruthenium, and compounds thereof, wherein theconcentration by weight of said at least one promoter in said catalystcomposition is less than the total concentration by weight of said zincand said titanium in said catalyst composition and wherein said catalystcomposition is prepared by calcining a mixture of zinc oxide andtitanium dioxide in the presence of molecular oxygen at a temperature inthe range of about 650° C. to about 1050° C. to form zinc titanate andadding said at least one promoter to said zinc titanate to form saidcatalyst composition.
 2. A composition in accordance with claim 1wherein the atomic ratio of zinc to titanium in said catalystcomposition is in the range of about 1:1 to about 3:1.
 3. A compositionin accordance with claim 1 wherein the atomic ratio of zinc to titaniumin said catalyst composition is in the range of about 1.8:1 to about2.2:1.
 4. A composition in accordance with claim 1 wherein said catalystcomposition has been calcined in the presence of molecular oxygen at atemperature in the range of about 500° C. to about 650° C. after said atleast one promoter has been added to said zinc titanate.
 5. Acomposition in accordance with claim 1 wherein the concentration ofvanadium, chromium, cobalt, nickel, molybdenum, or tungsten asindividual promoters, expressed as an element, if present, is in therange of about 0.1 to about 16 weight percent based on the weight ofsaid catalyst composition and the concentration of rhenium, palladium,rhodium, ruthenium or platinum as individual promoters, expressed as theelement, if present, is in the range of about 0.2 to about 1.6 weightpercent based on the weight of said catalyst composition.
 6. Acomposition in accordance with claim 5 wherein the total concentrationof any combination of the group from which said at least one promoter isselected, expressed as an element, is in the range of about 0.1 to about24 weight percent based on the weight of the catalyst composition.
 7. Acomposition in accordance with claim 1 wherein said at least onepromoter is cobalt and molybdenum.
 8. A composition in accordance withclaim 7 wherein the cobalt:molybdenum atomic ratio in said catalystcomposition is in the range of about 0.6:1 to about 0.8:1.
 9. Acomposition in accordance with claim 1 wherein said catalyst compositionis completely sulfided after said at least one promoter is added to saidzinc titanate.